The present invention relates generally to operations performed in subterranean wells and, in an embodiment described herein, more particularly provides apparatus and methods for underbalanced drilling and completion of wells.
There are several recognized advantages to drilling and completing a well in an underbalanced condition, that is, in a condition in which fluid pressure in a wellbore is less than fluid pressure in a formation intersected by the wellbore. For example, the underbalanced condition prevents fluid loss from the wellbore into the formation and prevents some types of damage to the formation which may be caused by infiltration of the wellbore fluid into the formation. An overview of underbalanced completion practices and their advantages may be found in an article entitled xe2x80x9cUnderbalanced Completions Improve Well Safety and Productivityxe2x80x9d by Tim Walker and Mark Hopmann (World Oil, November, 1995), which is incorporated herein by this reference.
Unfortunately, apparatus and methods which facilitate convenient, economical and safe underbalanced well operations are not presently widely available. For example, currently available apparatus designed to permit safe tripping in and out of drill strings and production tubing strings rely either on complex, expensive and unreliable mechanisms or on adapted surface-controlled devices, such as subsurface safety valves, which must be installed relatively near the surface or face a significant risk of damage to control lines attached thereto if installed relatively deep in the well. Thus, a need exists for apparatus which will safely and conveniently facilitate underbalanced well operations.
In particular, a need exists for a well control valve which is operable upon passage of a tool therethrough. The tool may be attached to a drill string, production tubing string, or other conveyance. In this manner, the valve may isolate a formation intersected by a wellbore in an underbalanced condition from the remainder of the wellbore while the tubular string is tripped in or out of the wellbore. The valve should be capable of being installed near the formation, without compromising its operability or reliability.
Where the valve is operated by applying a biasing force to the valve via a tubular string, and the tubular string includes a packer, the packer should be prevented from prematurely setting in the wellbore due to application of the biasing force. Therefore, it would be highly desirable to provide a packer setting tool which prevents premature setting of the packer, while also facilitating use of the packer in underbalanced well operations.
In carrying out the principles of the present invention, in accordance with an embodiment thereof, a well control valve and a packer setting tool are provided. The well control valve isolates one portion of a wellbore from the remainder of the wellbore, and does not require surface controls. The packer setting tool is hydraulically actuatable and prevents premature setting of a mechanical set packer attached thereto. Methods of underbalanced drilling and completion of wells are also provided.
The well control valve utilizes a colleted latch sleeve assembly which is displaceable in the valve to control opening and closing of a closure assembly. When a tool, such as a drill bit, is conveyed into the valve, a shifting device releasably secured on the tool engages the latch sleeve assembly. Further displacement of the tool causes displacement of the latch sleeve assembly to operate the closure assembly. When the closure assembly has been operated, the shifting device is released from the tool and deposited within the valve.
The packer setting tool includes an isolation sleeve which prevents fluid communication between an internal flow passage of the setting tool and a chamber in fluid communication with a setting piston. The packer setting tool also includes a circulation sleeve which permits fluid communication between the flow passage and the exterior of the setting tool, thereby permitting circulation through the setting tool when it is interconnected in a tubular string. A plugging device may be installed in the setting tool when it is desired to set a packer attached to the setting tool. Fluid pressure applied to the plugging device displaces the isolation sleeve, thereby permitting fluid communication between the flow passage and the chamber and permitting the packer to be set thereby, and displacing the circulation sleeve, thereby preventing circulation through the setting tool and permitting the packer to be tested after it is set.
These and other features, advantages, benefits and objects of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed descriptions of representative embodiments of the invention hereinbelow and the accompanying drawings.